Get Unable to cast object of type 'FFmpeg.NET.MediaFile' to type 'FFmpeg.NET.InputFile' error when trying to cut video file.

[zydjohnHotmail]

Hello:
I want to see if I can use this repo to cut one video (mp4 format).
I created one C# WinForms project (target .NET 5.0), add nuget package:
Install-Package xFFmpeg.NET -Version 6.0.0
The following is my C# code:
using FFmpeg.NET;
using System.IO;

public static async Task FFMPEG_Cut_Video1(string input_file1, string output_file1)
{
try
{
if (!File.Exists(input_file1))
{
Debug.Print("Input video not found, quit!");
return "FileNOTFound";
}
MediaFile video_in = new(input_file1);
MediaFile video_out = new(output_file1);
Engine ffmpeg = new(FFMPEG_Engine);
ConversionOptions options = new();
options.CutMedia(TimeSpan.FromSeconds(30), TimeSpan.FromSeconds(25));
await ffmpeg.ConvertAsync((InputFile)video_in, (OutputFile)video_out, options);
}
catch (InvalidCastException ex)
{
Debug.Print(ex.Message);
}
return "Cut_OK";
}

private async void Form1_Load(object sender, EventArgs e)
{
await FFMPEG_Cut_Video1("C:\Videos\1.mp4", "C:\Videos\cut1.mp4");
}

However, when I run my code, I got the following error:
System.InvalidCastException
HResult=0x80004002
Message=Unable to cast object of type 'FFmpeg.NET.MediaFile' to type 'FFmpeg.NET.InputFile'.
Source=System.Private.CoreLib
StackTrace:
at System.Runtime.CompilerServices.CastHelpers.ChkCast_Helper(Void* toTypeHnd, Object obj)
at System.Runtime.CompilerServices.CastHelpers.ChkCastClassSpecial(Void* toTypeHnd, Object obj)
at B20VideoSeekerSportRadarForm.Form1.<FFMPEG_Cut_Video1>d__7.MoveNext() in C:\Videos\VideoCut\Form1.cs:line 89
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at B20VideoSeekerSportRadarForm.Form1.<Form1_Load>d__8.MoveNext() in C:\Videos\VideoCut\Form1.cs:line 97

This exception was originally thrown at this call stack:
B20VideoSeekerSportRadarForm.Form1.FFMPEG_Cut_Video1(string, string) in Form1.cs
[External Code]
B20VideoSeekerSportRadarForm.Form1.Form1_Load(object, System.EventArgs) in Form1.cs
Please advise how I can fix this?
Using ffmpeg command, I can cut the video file, but I would like to use API in my C# program.
PS: I am using Windows 10 (Version 21H1), and Visual Studio 2019 (Version 16.10.4)
Thanks,

[DaveCS1]

Your code
MediaFile video_in = new(input_file1);
MediaFile video_out = new(output_file1);
needs to look as such
MediaFile video_in = new MediaFile(input_file1);
MediaFile video_out = new MediaFile(output_file1);

That's why you received the type mismatch error.

//ffmpegPath is your path to ffmpeg.exe. eg "c:\ffmpeg\ffmpeg.exe"
public async Task MakeVideoSegment(string input, string output, string ffmpegPath, int TrimStart, int TrimEnd)
{
var inputFile = new MediaFile(input);
var outputFile = new MediaFile(output);
var ffmpeg = new FFmpeg.NET.Engine(ffmpegPath);
var options = new ConversionOptions();
int SecondsToTrim = TrimEnd - TrimStart;
options.CutMedia(TimeSpan.FromSeconds(TrimStart), TimeSpan.FromSeconds(SecondsToTrim));
await ffmpeg.ConvertAsync(inputFile, outputFile, options);
TrimmedFileNameFullPath = outputFile.FileInfo.FullName.ToString();
return TrimmedFileNameFullPath;

    }

[cmxl]

Use InputFile and OutputFile instead of MediaFile. MediaFile will now actually become an abstract class and does not implement IInputArguments which is used by ConvertAsync.

var inputFile = new InputFile(@"C:\Path\To_Video.flv");
var outputFile = new OutputFile(@"C:\Path\To_Save_ExtractedVideo.flv");
var ffmpeg = new Engine("C:\ffmpeg\ffmpeg.exe");
var options = new ConversionOptions();
options.CutMedia(TimeSpan.FromSeconds(30), TimeSpan.FromSeconds(25));
await ffmpeg.ConvertAsync(inputFile, outputFile, options, default);